<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <form action="xdf">
        性别：
    <select name="sex" id="sex">
        <option value="nan">男</option>
        <option value="nv">女</option>
    </select>
    <input type="submit">
    </form>
    
</body>
</html>